燃煤电厂200 t /d生活垃圾无氧热解耦合协同处置优化

Optimization on 200 t / d garbage co⁃utilization in a coal⁃fired power plant through air⁃free pyrolysis process

  • 摘要: 随着我国城市生活垃圾的逐年增长,生活垃圾的减量化无害化处理变得越来越迫切。相比于填埋、焚烧等传统垃圾处理方式,热解法处理生活垃圾具有二噁英排放量少,二次污染小等优势,近年来受到了越来越多研究者的关注。针对我国县镇级别的垃圾处理需求,提出了一种新的生活垃圾热解耦合燃煤电厂协同处置的工艺路线,并结合现场实验数据,针对某55 MW燃煤机组耦合200 t/d垃圾的实际案例,利用Aspen plus软件对该工艺流程进行了验证和模拟。试验和模拟结果表明:在不抽取燃煤锅炉烟气的条件下,可以通过燃烧部分垃圾无氧热解产生的油气作为垃圾干化和热解过程所需的热源,并且还有部分富余的高热值热解油气的可送入燃煤机组燃烧。当抽取部分燃煤锅炉中高温烟气用于垃圾干燥和热解过程时,垃圾无氧热解可富余更多的高热值油气用于燃煤锅炉助燃调峰;同时,垃圾热解产生的高氯垃圾炭可以直接送进锅炉燃烧。对55MW燃煤机组耦合垃圾炭产生的二噁英进行了现场检测,试验发现:当不掺烧垃圾炭时,烟气中二噁英总含量为0.0061 ng TEQ/m3;当垃圾炭掺烧比为1%时,烟气中二噁英总含量为0.0053 ng TEQ/m3,二噁英含量在掺烧前后没有显著的变化,且远低于地方排放标准。干燥过程的高湿烟气再循环后进入油气燃烧热风炉,有利于提高耦合系统的富余热解油气。考虑到烟气输送安全,实际抽取锅炉烟气温度低于热解油气燃烧温度,故对本案例(55 MW机组耦合200 t/d垃圾)实际的最大锅炉烟气抽取量最大不超过锅炉总烟气量的2%,对锅炉总体性能的影响不显著。

     

    Abstract: With the gradual growth of urban garbage amount in China,the reduction and harmless treatment of gar⁃ bage has become more and more urgent. Compared with the traditional waste treatment methods such as landfill and incineration,the pyrolysis treatment of garbage has the advantages of less dioxin emission and less secondary pollution,and has received more and more attention from researchers in recent years. A new process route of co⁃utilization of gar⁃ bage coupled with coal⁃fired power plants was proposed for the needs of waste treatment at the county and township level in China. Combined with the field experimental data,aiming at the actual case of a 55 MW coal⁃fired unit cou⁃ pled with 200 t / d garbage,the process was verified and simulated by Aspen plus software. The experimental and simu⁃ lation results show that without extracting flue gas from coal⁃fired boilers,the tar and gas produced by the anaerobic pyrolysis of garbage can be burned as a heat source for drying and pyrolysis. And part of the surplus high calorific val⁃ ue pyrolysis oil and gas can be sent to coal⁃fired units for combustion. When part of the middle and high temperature coal⁃fired flue gas is extracted for the garbage drying and pyrolysis process,the anaerobic pyrolysis of gar⁃ bage can spare more high⁃calorific value oil and gas for combustion⁃supporting and peak shaving. At the same time,the high⁃chlorine garbage charcoal produced by garbage pyrolysis can be directly sent to the boiler for combus⁃ tion. The on⁃site detection of dioxins produced by 55 MW coal⁃fired units coupled with garbage charcoal was carried out. When the garbage charcoal was not mixed,the total dioxin content in the flue gas was 0.006 1 ng TEQ/ m3 . When the garbage charcoal mixing ratio was 1%,the total dioxin content in the flue gas was 0.005 3 ng TEQ / m3 . The dioxin content did not change significantly before and after mixing,and was far below the local emission standard. The high⁃humidity flue gas in the drying process was recirculated into the oil and gas combustion hot blast stove,which is beneficial to improve the surplus pyrolysis oil and gas of the coupling system. Considering the safety of flue gas transportation,the actual extracted boiler flue gas temperature is lower than the combustion temperature of pyrolysis oil and gas, so the actual maximum extracted boiler flue gas volume in this case ( 55 MW unit coupled with 200 t / d garbage) is no more than 2% of the total boiler flue gas volume,which has no significant impact on the overall performance of the boiler.

     

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